It has previously been proposed to drive centrifugal compressors from the exhaust gases from an internal combustion engine by coupling an exhaust gas turbine to the radial compressor. In addition, the engine shaft itself can be coupled to an auxiliary compressor to generate compressed air, for example having a pressure in the range of about 2 to 4 bar. If the engine operates under conditions of low air supply, the air compressed by the auxiliary compressor is introduced as an additional supply leading the so-compressed air to a chamber of the centrifugal compressor. The supply line, usually, also includes a check valve so that only air from the auxiliary compressor can be admitted into the chamber of the compressor housing. The chamber from the compressor housing then leads to a plurality of nozzles which are located about the circumference of the centrifugal compressor to admit the air compressed by the auxiliary compressor to the drive vanes of the centrifugal compressor.
A system of this type is described, for example, in German Pat. No. 15 03 581 to which U.S. Pat. No. 3,462,071 corresponds. In the so-described system, a centrifugal compressor is shown driven by an exhaust gas turbine. The auxiliary compressor generates compressed air in the order of 2 to 4 bar which is conducted, via a check valve, into the housing of the centrifugal compressor.
The patent is silent regarding the connection of the auxiliary compressor and its activation or control to the internal combustion engine.